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[2003:cb:c704:1000:21d5:831d:e107:fbd6]) by smtp.gmail.com with ESMTPSA id l27-20020a05600c2cdb00b003a84375d0d1sm42034036wmc.44.2023.01.16.02.53.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 16 Jan 2023 02:53:01 -0800 (PST) Message-ID: <916aedc8-1d0b-a0f9-5ddf-6c6305e7cbdb@redhat.com> Date: Mon, 16 Jan 2023 11:53:00 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [PATCH v3] mm/page_ext: Do not allocate space for page_ext->flags if not needed To: Vlastimil Babka , Pasha Tatashin , akpm@linux-foundation.org, mhocko@suse.com, quic_charante@quicinc.com, lizhe.67@bytedance.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Mike Rapoport References: <20230113154253.92480-1-pasha.tatashin@soleen.com> <0c706897-b2cc-714c-c72e-4154b1f3f52b@suse.cz> From: David Hildenbrand Organization: Red Hat In-Reply-To: <0c706897-b2cc-714c-c72e-4154b1f3f52b@suse.cz> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 6209C80017 X-Stat-Signature: dicp1xzpm3dterpd33g8d79hrgm3fxmt X-HE-Tag: 1673866385-319308 X-HE-Meta: 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 Xfe7vNuW 7yBjYCZxVUOFMNVWX5EtZ349YmY0dn+p3g0OF/6DxUgTe908v9nIMp3SRaoFHpcpDRSRXuYoP1ZRAt5xyZxRYS2fXubWG+xYX++gnvvvUJRj3BHklSnwIjG2167tgq45U13hajXl72dZ/pMT+b7wtQXlpKoAdlhf+FNShjw4mcWIMVWxErAsX3kKcQ0qsM07fE0RS X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 16.01.23 11:51, Vlastimil Babka wrote: > On 1/13/23 16:42, Pasha Tatashin wrote: >> There is 8 byte page_ext->flags field allocated per page whenever >> CONFIG_PAGE_EXTENSION is enabled. However, not every user of page_ext >> uses flags. Therefore, check whether flags is needed at least by one >> user and if so allocate space for it. >> >> For example when page_table_check is enabled, on a machine with 128G >> of memory before the fix: >> >> [ 2.244288] allocated 536870912 bytes of page_ext >> after the fix: >> [ 2.160154] allocated 268435456 bytes of page_ext >> >> Also, add a comment before page_ext_operations that describes the >> field, and remove check if need() is set, as that is now a required >> field. >> >> Signed-off-by: Pasha Tatashin > > Acked-by: Vlastimil Babka > > Mike's comments look reasonable to me. Seconded Acked-by: David Hildenbrand -- Thanks, David / dhildenb